When electrical connection is established by means of a conventional connector, means for preventing interfering waves from entering a signal to be transmitted or for removing spurious signals has to be employed independently of the connector. Namely, a plurality of capacitors each having a through-hole therein, are connected to corresponding conductors extending from such a conventional connector as will be described in detail with reference to drawings. The combination of such a conventional connector and the above mentioned capacitors requires a relatively large space, while being time consuming to install the capacitors and to solder the terminals of the capacitors with the conductors of the connector. Furthermore, the suppression or elimination of noises cannot be sufficiently achieved with such a combination.